The long-term objective of this research is to understand the generation and control of movement in the vertebrate nervous system. Due to its relative simplicity, the lamprey nervous system is an important model for investigating motor control in vertebrates. This particular project will examine how the lamprey spinal cord informs the brain of the spinal motor commands and of the sensory consequences of those commands. This information ensures that the brain's descending control of the spinal cord is having the desired outcome and is occurring in a context-appropriate manner. This project will identify and characterize spinal neurons that have axons projecting to the brainstem (spinobulbar neurons). The specific aims are to answer four questions regarding the functional roles of these cells. 1) Can spinobulbar neurons be divided into two classes of sensory-related and locomotor network-related types? 2) Are spinobulbar neurons specialized only for transmission of information to the brain or do they also make synaptic connections in the spinal cord? (3) Do spinobulbar neurons make direct synaptic connections with reticulospinal neurons or do they act via local brainstem interneurons? (4) Do spinobulbar neurons receive synaptic input from the same reticulospinal cells upon which they synapse? The membrane potential of spinobulbar neurons will be recorded with intracellular microelectrodes in the isolated brainstem-spinal cord preparation, and these recordings will be used to characterize the electrical and morphological properties of the cells and their synaptic inputs and outputs. Understanding how the spinal cord and the brainstem interact is fundamental to understanding the mechanisms of motor control and will be important for the development of effective therapeutic measures for treating human disease and injury of the motor system.